1. Field of the Invention
The present invention relates to a robot controller for making teaching work easier.
2. Description of the Related Art
One method of teaching a robot is direct teaching where a robot is manually operated so as to be taught each teaching point. In this method, an operator selectively teaches the teaching points while monitoring the positional relationship of tools attached to the wrist of the robot and the workpiece.
However, when, for example, a position at the lower part of the body of a vehicle is to be taught as a position for spot welding, it is probable that this position to be taught cannot be seen. Conventionally, with teaching of places where the positional relationship between the robot tools and the workpiece is difficult to discern, teaching of such teaching points has relied upon the intuition of the operator. When teaching a contact position of a tool and a workpiece, the contact conditions are discerned by the operator. When a location is difficult to see, methods as described above where teaching is carried out relying upon the intuition of the operator or where the operate teaches while looking with a lamp to be aware of contact between tools and a workpiece are also put into practice.
In cases where a position is taught where a robot (tool) should be moved in a fixed direction by a fixed amount from a current position, conventionally a method has been adopted where a manual operation is carried out while the operator confirms the current position of the robot (tool), the robot (tool) is moved up to the teaching position, the desired distance of operation is added to the current position and the teaching position is directly obtained.
There are also cases where it is preferable to change the position or posture of a tool by performing a manual feed operation to the position where the tool is to be moved, taking the tool center point as a reference. In this case, conventionally, the tool coordinate system is reset every time the position where the tool center point is set is moved. Further, when a teaching point is taught where a tool is brought into contact with or brought close to the workpiece in a fixed posture, the operator operates the tool until the desired posture is obtained using a manual feeding.
However, relying on the intuition of the operator for teaching positions that are difficult to see invites inaccuracy in the teaching positions and teaching work therefore becomes difficult. Further, in the case of teaching a position of contact of the workpiece and the tool, variations in teaching position occur and reliable teaching work is difficult when teaching relies upon the intuition of the operator or when the operator carries out teaching while monitoring the contact position of a workpiece and a tool using a lamp.
In the case of operations of a fixed amount in a fixed direction from a current position, with methods where a teaching position is obtained from manual feeding by the operator or by adding to a current position a distance to be moved, variations in the teaching position occur and teaching work becomes complex. Further, resetting a tool coordinate system every time the tool center point moves when changing the tool posture taking the tool center point as a reference, or obtaining a posture of the tool through manual operation when bringing a tool into contact with or close to a workpiece in a fixed posture also makes teaching work complicated.